Abstract
OBJECTIVE: To evaluate associations between iron supplementation and iron deficiency in infancy and internalizing, externalizing, and social problems in adolescence. STUDY DESIGN: The study is a follow-up of infants as adolescents from working-class communities around Santiago, Chile who participated in a preventive trial of iron supplementation at 6 months of age. Inclusionary criteria included birth weight ≥3.0 kg, healthy singleton term birth, vaginal delivery, and a stable caregiver. Iron status was assessed at 12 and 18 months of age. At 11-17 years of age, internalizing, externalizing, and social problems were reported by 1018 adolescents with the Youth Self Report and by parents with the Child Behavior Checklist. RESULTS: Adolescents who received iron supplementation in infancy had greater self-reported attention-deficit/hyperactivity disorder but lower parent-reported conduct disorder symptoms than those who did not (Ps < .05). Iron deficiency with or without anemia at 12 or 18 months of age predicted greater adolescent behavior problems compared with iron sufficiency: more adolescent-reported anxiety and social problems, and parent-reported social, post-traumatic stress disorder, attention-deficit/hyperactivity disorder, oppositional defiant, conduct, aggression, and rule breaking problems (Ps < .05). The threshold was iron deficiency with or without anemia for each of these outcomes. CONCLUSIONS: Iron deficiency with or without anemia in infancy was associated with increased internalizing, externalizing, and social problems in adolescence.